Approaches for Determining Swale Performance for Stormwater Runoff

Swales are "engineered vegetated ditches" that provide stable routing for stormwater runoff and a low-cost drainage option for highways, farms, industrial sites, and commercial areas. It is reported in the literature that swales mitigate runoff-carried pollutants, reduce runoff volume, and reduce peak stormwater runoff rate that can damage low-order streams and transfer pollutant loads carried in the runoff to receiving waters. EPA recognizes the reported capabilities of swales to reduce the environmental footprint while meeting the practical need to manage stormwater runoff. Further research, however, is needed to provide a more complete understanding of swales operations. This paper introduces EPA's swale research strategy, lessons learned during swale construction, and initial results of media and water balance trials. By developing a more complete understanding of the functions and capabilities of swales, it is hoped that the user community will be equipped to design and construct swales that efficiently reduce pollutant loading and protect receiving waters. Outcomes of this research are expected to help managers and regulators meet designated uses and goals outlined in the Clean Water Act, and maintain a continuing supply of high-quality water for human and aquatic life and economic growth.